More than anything, they're meant to scare drivers into keeping sober when behind the wheel, said Jerry McCory, director of Indiana's Council on Impaired and Dangerous Driving.

The 300 yellow signs across Indiana are part of a national effort targeting drunken driving over the three summer weekends that are traditionally the deadliest of the year.

Each state has received federal money for the campaign to curb drunken driving, which lasts through July 13. The National Highway Traffic and Safety Administration also is spending $11 million on television commercials to promote the national campaign.

Alaska, using the slogan "Drive Hammered, Get Nailed," is funneling its federal money for additional police patrols looking specifically for drunken drivers as part of the 17-day effort. Many other states are using sobriety checkpoints, or a combination of patrols and checkpoints.

AAA estimated that 36.8 million people were expected to travel the nation's highways during this year's 4th of July weekend, which would be the highest total in nine years.

The highway administration estimated 560 deaths will occur on the nation's roadways during the weekend, and a majority _ 55 percent _ will involve alcohol.

Indiana's effort includes the billboards, as well as increase in actual sobriety checkpoints and patrols looking specifically for drunken drivers. The state received about $2.5 million in federal money for such efforts this year, McCory said.

The billboards, posted over the last two weeks, have caught motorists' attention. Georgenne Lollar, 69, said too many people drink and drive.

"That ought to wake some of them up," Lollar said of a billboard overlooking a busy Indianapolis street. "I hope they catch them all."